The invention relates to a process for the preparation of trifluoromethyl acetophenone derivatives of formula I 
wherein:
Y is a group that is inert for the reactions, preferably a hydrocarbyl; and
m is from 0 to 4; preferably 0; in which process
a) a compound of formula II 
wherein
X is chlorine, bromine or iodine, preferably bromine, and
Y and m are as defined for formula I,
is reacted with a vinylether of formula IIIa or an enamide of formula IIIb
CH2xe2x95x90CHxe2x80x94OR1xe2x80x83xe2x80x83(IIIa)
CH2xe2x95x90CHxe2x80x94N(R2)xe2x80x94COxe2x80x94R3xe2x80x83xe2x80x83(IIIb)
wherein R1 and R2 are each independently of the other C1-C8alkyl, C2-C8alkenyl, C1-C8alkoxyalkyl, C3-C6cycloalkyl, phenyl-C1-C2alkyl or C1-C8acyl, which groups are optionally substituted,
R3 is C1-C8alkyl, C2-C8alkenyl, C1-C8alkoxyalkyl, C3-C6cycloalkyl or phenyl-C1-C2alkyl, which groups are optionally substituted,
in a solvent, in the presence of a base and of a catalytic amount of a palladium compound comprising a monodental or bidental phosphine ligand;
b) the resulting intermediate of formula IVa and IVb resp. 
is hydrolyzed to the compound of formula I.
These compounds are important intermediates for the preparation of pharmaceuticals, pesticides, dyestuffs, perfumes and other products.
The palladium catalyzed vinylation of aromatic halogen compounds is the well known xe2x80x9cHeckxe2x80x9d-reaction. In this reaction, vinyl ethers can react in (a) or in (b) position, resulting in compounds A and B respectively, as shown the scheme 1. Only compound A can be hydrolyzed to the acetophenone C. Thus, for the preparation of acetophenones by the xe2x80x9cHeckxe2x80x9d-reaction, the initial vinylation reaction should predominantly occur in (a) position. 
EP-A-688,757 discloses the vinylation of halogen benzene derivatives in the presence of a palladium/phosphine catalyst; the regioselectivity of the reaction with respect to the vinyl group is not discussed therein, but according to the working examples the vinyl group reacts predominantly in (b) position. The preparation of acetophenones by palladium catalyzed reaction of aryl halides with vinyl ethers is described in J. Org. Chem. Vol.52, 1987, 3529-3536. The regioselectivity of this reaction is dependent, amongst others, on the catalyst and the substituent on the aryl group. Substitution at (a)-position is increased by adding phosphine ligands to the palladium catalyst (J. Org. Chem. Vol.57, 1992, 1481-1486), whereas electron withdrawing groups on the aryl moiety favour substitution at (b)-position (J. Org. Chem. Vol.52, 1987, 3529-3536). Accordingly, the strongly electron withdrawing trifluoromethyl group is expected to favour substitution at (b)-position over (a)-position resulting in low yields of trifluoromethyl acetophenone. Surprisingly it has been found that a high ratio of (a)-substitution over (b)-substitution can be obtained in the reaction according to this invention, resulting after hydrolysis in good yields of the corresponding trifluoromethyl acetophenone. The method provided herewith is distinguished by ready availability of the starting materials, good technical feasibility and is economically and ecologically favorable. The groups R1, R2 and R3 may be substituted by any functional group which does not negatively affect the reaction; examples are C1-C8alkyl, halo-C1-C8alkyl, C2-C8alkenyl, halo-C2-C8alkenyl, C1C8alkoxyalkyl, C3-C6cycloalkyl, phenyl, phenoxy, phenyl-C1-C2alkyl, hetaryl, hetaryloxy or C1-C8acyl.
Suitable palladium compounds which can be used as catalysts are for example palladium bis-(dibenzalacetone)-palladium, palladium acetate, palladium dichloride, palladium dibromide, palladium trifluoroacetate, palladium diphosphine halogenide complexes and acetate complexes as palladium-bis(triphenylphosphine) dichloride and palladium-bis(triphenylphosphine) acetate; further on palladium tetrachloro complexes; preferred is bis-(dibenzalacetone)-palladium. Suitable phosphine ligands are aryl phosphines as triphenyl phosphine, methyl diphenylphosphine or 1,3-bis-(diphenylphosphino)-propane, preferably triphenyl phosphine. The amount of palladium catalyst is 0.01 to 10 mol %, preferably 0.1 to 1 mol % in relation to the compound of formula II.
The molar ratio of palladium to phosphine is from 1:1 to 1:4, preferably ca. 1:2.
Suitable solvents for reaction step a) are aprotic, polar solvents, preferably propylene carbonate, anisole, N-methyl-2-pyrrolidone, N,N-dimethyl acetamide, dimethylformamide, tetramethylurea, gamma-butyrolacone, N,N-dimethylimidazolidinon and dimethyl sulfoxide.
Suitable bases are amines, as triethylamine, triethylenediamine, cyclohexylamine, N-cyclohexyl-N,N-dimethyl-amine, N,N-diethylaniline, pyridine, 4-(N,N-dimethylamino)pyridine, N-methylmorpholine and 1,8-diazabicyclo[5.4.0]undec-5-ene (DBU); alkali metal or alkaline earth metal hydroxides, carbonates, hydrogencarbonates and phosphates, preferably potassium salts; or salts of carboxylic acids, preferably alkali salts of C2-C4carboxylic acids. Preferred are triethylamine, potassium hydroxide, -carbonate,-hydrogencarbonate and -phosphate, and sodium acetate; particularly preferred is triethylamine.
Reaction step a) is carried out at from 50xc2x0 C. to 200xc2x0 C., preferably from 70xc2x0 C. to 150xc2x0 C.; most preferably from 90xc2x0 C. to 120xc2x0 C. Reaction step b) (hydrolysis) is carried out with diluted acid, as hydrochloric acid, sulfuric acid or acetic acid, preferably in mixture with a solvent, wherein the product is soluble. The temperature is not critical and may vary from 0xc2x0 C. to +70xc2x0 C.
Preferred is the preparation of 3-trifluoromethylacetophenone, wherein 3-bromo-benzotrifluorid is reacted with a vinylether of formula IIIa
CH2xe2x95x90CHxe2x80x94OR1xe2x80x83xe2x80x83(IIIa)
wherein R1is C1-C8alkyl; preferably C4-C6alkyl.